KANSAS CITY, Mo. -- Investigators believe alcohol, and stress in the relationship between Jovan Belcher and his girlfriend, Kasandra Perkins, played roles in Belcher killing Perkins and then himself, a Kansas City, Mo., police source said Tuesday.

Before the Saturday morning murder-suicide, police said, the Kansas City Chiefs provided couples counseling to Belcher, 25, a linebacker from West Babylon, and Perkins, 22.

Friends of Perkins have said there was tension between the two that escalated after the birth of their daughter, now 3 months old, and a police source said the two argued about money.

In other revelations that came out Tuesday from Kansas City police, they said Belcher's mother -- who had been at his home visiting -- described the scene after the shooting. She said Belcher knelt down in the master bedroom of the house the couple shared, and kissed his slain girlfriend on the forehead, saying, "I'm sorry," police said.

Then, police said, Belcher kissed their daughter, Zoey, apologized to his mother, and drove his Bentley to Arrowhead Stadium about 8 a.m. There, police said, Belcher told Chiefs coach Romeo Crennel and other team officials "I have to do this," before kneeling behind a vehicle, crossing himself and firing the shot that ended his life.

In a transcript of the 911 call Belcher's mother, Cheryl Shepherd, made to police, she says of Perkins, "She's still breathing but please hurry. I don't know how much time she's got."

With the baby crying in the background, the police dispatcher is heard asking where Belcher is. Shepherd answers: "He left." The dispatcher asks: "OK, they were arguing and he shot her?" and she answers, "Yes, [they] were arguing."

On Monday, police investigators said they had talked to witnesses who saw Belcher at several bars in the trendy downtown Power and Light District Friday night, and he appeared intoxicated hours before the shootings.

Tuesday, a police official said a 911 call was received around 2:50 a.m. Saturday from someone reporting a suspicious car with a man inside, outside an apartment building on the 700 block of East Armour Boulevard. Responding officers found Belcher asleep in his car and asked him to show them identification, which police said he did.

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The officers said Belcher was intoxicated, according to Kansas City police spokesman Darrin Sapp. "They said they could tell he'd been drinking," he said.

Police said Belcher told officers he was waiting for his "girlfriend" -- not Perkins, but another woman -- who lived in the building, and he called her at their request. Someone then let Belcher in, police said, and he stayed there before going home.

A woman who identified herself as Brittni Glass, an alias, said she was out with Belcher the night before the shootings, saying: " We just went out. Nothing was wrong. It's just a tragedy."